1. Field of the Invention
The present invention relates to an automatic sheet-feeding device of a printer, and more particularly, to an automatic sheet-feeding device of a printer which separates a plurality of stacked recording sheets one by one and subjects the recording sheets to printing.
2. Description of the Related Art
In general, various types of printers, such as thermal transfer printers and ink-jet printers, are used as output devices for computers, word processors, facsimile machines, and the like.
In order to perform desired printing in such printers, a plurality of recording sheets are loaded on a sheet loading section mounted on a printer frame, and are separated and supplied one by one by rotating delivery rollers in contact with the uppermost recording sheet. The recording sheet supplied by the delivery rollers is further conveyed by the rotational force of feeding rollers provided ahead of the printing position in the printer, that is, the feeding rollers take over the role of feeding the recording sheet from the delivery rollers.
As shown in FIG. 6, a printer 101 to which a conventional automatic sheet-feeding device is applied is configured such that printing is performed while a recording sheet 100 is fed substantially vertically. In this printer 101, a platen 104 shaped like a flat plate extends in the widthwise direction of a printer frame 103 so that the surface of the recording sheet 100 to be printed is held substantially vertically. On one side of the printer frame 103, a carriage 105 is disposed so as to be reciprocally moved along the platen 104 by a driving mechanism (not shown). At one end (the right side in FIG. 6) of the carriage 105, a thermal head 123 having an array of heating elements (not shown) is disposed so as to be moved closer to and further apart from the platen 104 by a driving mechanism (not shown).
A ribbon cassette is detachably mounted on the carriage 105. The thermal head 123 is pressed against the platen 104 while the recording sheet 100 and an ink ribbon contained in the ribbon cassette are supplied between the platen 104 and the thermal head 123.
At the center of the printer frame 103, a delivery roller driving shaft 111 extends in the widthwise direction of the printer frame 103 and is supported by the printer frame 103 at both ends. A plurality of delivery rollers 114 are mounted in the axial direction on the delivery roller driving shaft 111 at predetermined intervals.
A cam lever 112 is mounted at the axial end of the delivery roller driving shaft 111 to corotate therewith.
A sheet loading section support shaft 124 is disposed in the upper part of the printer frame 103 on the upstream side in the sheet feeding direction. The sheet loading section support shaft 124 pivotally supports a sheet loading section 125 which has an upper surface functioning as a sheet stacking plate 107 on which a plurality of recording sheets 100 are stacked. When the sheet loading section 125 is pivoted in the sheet feeding direction, the front part of the sheet stacking plate 107 can be pressed against the delivery rollers 114 by an urging means 113 such as a spring member.
A protuberance 126 is formed at the lower end of the sheet stacking plate 107 of the sheet loading section 125. The leading end of the cam lever 112 can either be engaged with or disengaged from the protuberance 126 depending on the rotation of the delivery rollers 114.
A separating plate 120 is disposed below the delivery rollers 114, and the leading edges of the recording sheets 100 placed on the sheet stacking plate 107 make contact with the separating plate 120. The separating plate 120 is inclined at a predetermined angle so that only the uppermost recording sheet 100 is separated.
A feeding roller driving shaft 116 is disposed below the platen 104 and on the side diagonally above the delivery roller driving shaft 111 so as to extend in the widthwise direction and to be supported by the printer frame 103 at both ends. A plurality of feeding rollers 117 are mounted on the feeding roller driving shaft 116 at predetermined intervals. On the side diagonally below the feeding rollers 117, auxiliary rollers 118 are disposed so that they are in contact with the outer peripheral surfaces of the feeding rollers 117 so as to corotate therewith. Between the sheet loading section 125 mounted in the printer frame 103 and the feeding rollers 117, a curved guide plate 119 is formed so as to guide recording sheets 100 supplied from the sheet loading section 125 by the delivery rollers 114 between the feeding rollers 117 and the auxiliary rollers 118 placed on the downstream side in the sheet feeding direction.
On the downstream side of the platen 104 in the sheet feeding direction, a discharge-roller driving shaft 121 rotatably extends in the widthwise direction of the printer frame 103 and is supported by the printer frame 103. A plurality of discharge rollers 122 are mounted on the discharge-roller driving shaft 121 at predetermined intervals so as to discharge recording sheets 100, which have been subjected to printing, outside.
In this way, a recording sheet 100 delivered from the sheet loading section 125 by the delivery rollers 114 is guided by the guide plate 119 and is transferred to the feeding rollers 117 and the auxiliary rollers 118 ahead of the printing position, and is conveyed upward to the printing position while being pinched therebetween. The printed recording sheet 100 is discharged from the printer 101 by the discharge rollers 122.
In the automatic sheet-feeding device of the printer with such a configuration, the upper side of the sheet loading section 125 is pivoted away from the platen 104 against the urging force of the urging means 113 so that the sheet loading section 125 separates from the delivery rollers 114. In this state, recording sheets 100 are placed on the sheet stacking plate 107 while the leading edges thereof slide on the upper surface of the sheet stacking plate 107 from above.
Then, the sheet loading section 125 is pivoted again by the urging force of the urging means 113 so that the sheet stacking plate 107 moves closer to the platen 104, whereby the protuberance 126 of the sheet loading section 125 and the cam lever 112 of the delivery rollers 114 are brought into contact with each other. Subsequently, an automatic sheet supply operation and a printing operation of the printer 101 are started, and only the uppermost recording sheet 100 placed on the sheet stacking plate 107 is conveyed toward the feeding rollers 117 by the rotation of the delivery rollers 114.
The conveyed recording sheet 100 is guided by the guide plate 119 and is transferred between the feeding rollers 117 and the auxiliary rollers 118.
Subsequently, the recording sheet 100 is fed back to the upstream side in the sheet feeding direction by reversely rotating the feeding rollers 117, and is cued up to a printing start position.
After the recording sheet 100 has been cued up to the printing start position, desired printing is performed thereon by pressing the thermal head 123 against the platen 104 with the ink ribbon and the recording sheet 100 therebetween and by selectively driving the heating elements of the thermal head 123 according to printing information, such as image information, while moving the carriage 105 along the platen 104.
In the printer 101 to which the conventional automatic sheet-feeding device is applied, when a plurality of recording sheets are loaded on the sheet stacking plate 107 of the sheet loading section 125, the delivery rollers 114 are separate from the sheet loading section 125.
In this case, the delivery roller driving shaft 111 with the delivery rollers 114 thereon is fixed to the printer frame 103, and the sheet stacking plate 107 is pivoted downward on the sheet loading section support shaft 124. Since reliability of loading the recording sheets 100 is ensured by minimizing the amount of release of the delivery rollers 114 and the sheet stacking plate 107, when approximately twenty to thirty recording sheets 100 are inserted into the sheet stacking plate 107, they abut against the surrounding components, thereby making insertion difficult.
In such a case, in order to load such a large number of recording sheets 100 on the sheet stacking plate 107 more easily, the sheet stacking plate 107 must be manually pressed down.
When the amount of release of the delivery rollers 114 and the sheet stacking plate 107 is increased in order for the recording sheets 100 to be loaded more easily on the sheet stacking plate 107 of the sheet loading section 125, the recording sheets 100 may be inadvertently inserted in the sheet feeding direction through the space formed therebetween.
When the uppermost recording sheet 100 stacked on the sheet stacking plate 107 is subjected to printing, it is conveyed in the sheet feeding direction only by the feeding rollers 117 in a state while the delivery rollers 114 are separate from the sheet loading section 125 in order to increase the sheet feeding accuracy.
Therefore, in such a case where loading is made easier by increasing the amount of release of the delivery rollers 114 and the sheet stacking plate 107, the uppermost recording sheet 100 placed on the sheet stacking plate 107 may slip in the sheet feeding direction although its movement in that direction is limited by the separating plate 120. In particular, when several tens of recording sheets are stacked, such an undesirable result will occur frequently.
Accordingly, it is an object of the present invention to provide an automatic sheet-feeding device of a printer in which recording sheets can be reliably loaded in a sheet loading section and only the uppermost recording sheet is reliably supplied during a sheet supply operation.
In order to overcome at least one of the above problems, according to an aspect of the present invention, there is provided an automatic sheet-feeding device of a printer including a sheet loading section for holding a plurality of stacked recording sheets to be subjected to printing; a delivery roller movable closer to and further apart from the recording sheets held in the sheet loading section so as to supply the recording sheets in the sheet feeding direction; and a separating plate disposed at the lower end of the sheet loading section so as to allow the leading edges of the recording sheets to contact therewith and to separate the uppermost recording sheet one by one, wherein the delivery roller is rotationally driven while it is in contact with the sheet loading section and the inclination of the separating plate with respect to the surface of the sheet loading section is made large enough to separate the uppermost recording sheet one by one when the recording sheets held in the sheet loading section are supplied, and the delivery roller is separated from the sheet loading section and the inclination of the separating plate with respect to the surface of the sheet loading section is made small enough to hold the recording sheets except when the recording sheets are supplied from the sheet loading section.
In this case, since the separating plate functions as a barrier in the sheet feeding direction when the recording sheets are loaded on the sheet loading section, they will not be inadvertently inserted from the sheet loading section in the sheet feeding direction serving as the inserting direction, and reliability of loading the recording sheets on the sheet loading section can thereby be improved.
Even when several tens of recording sheets are inserted together in the sheet loading section, they do not abut against the surrounding components because space, large enough to hold the recording sheets, is ensured between the sheet loading section and the delivery roller. This also improves reliability of loading the recording sheets.
Preferably, the separating plate is moved in connection with the movement of the delivery roller closer to and further apart from the sheet loading section.
During the operation of printing on a recording sheet, recording sheets remaining on the sheet loading section are limited by the separating plate inclined at a small angle, and therefore, will not be supplied in the sheet feeding direction while overlapping with each other.
Preferably, the automatic sheet-feeding device of a printer further includes a rotation shaft for rotatably supporting the delivery roller, and a lever arm pivotally movable on one end so as to support the rotation shaft at the other end. The lever arm has a retaining portion protruding outward for supporting the separating plate. When the delivery roller performs a sheet supply operation, the separating plate increases its angle of inclination via the retaining portion of the lever arm in connection with the movement of the delivery roller into contact with the recording sheets on the sheet loading section. Except during the sheet supply operation, the separating plate decreases its angle of inclination via the retaining portion of the lever arm in accordance with the movement of the delivery roller further apart from the sheet loading section.
In this case, since the separating plate automatically adjusts its angle of inclination to predetermined angles in accordance with the movement of the delivery roller, troublesome operations and incorrect operations can be avoided.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments (with reference to the attached drawings).